MongoDB Associate DBA Most trusted Questions 2023
MongoDB Associate DBA Most trusted Questions 2023
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Question 1:
In the context of MongoDB‘s Role-Based Access Control (RBAC), which of the following built-in roles is specifically designed to grant a user the privileges needed to create and modify the database‘s design, but does not permit any data modification actions on the existing data?
A. userAdmin
B. dbAdmin
C. read
D. dbOwner
Answer: B
Explanation:
The dbAdmin role provides the ability to view and modify the database‘s design and perform maintenance operations, but it does not permit any data modification actions on existing data.
read -> Incorrect. The read role provides the ability to read data from collections, use indexes, and perform certain non-modifying actions on the database. This role does not permit the modification of the database‘s design or structure.
dbOwner -> Incorrect. The dbOwner role combines the privileges granted by the readWrite, dbAdmin, and userAdmin roles. A user granted this role can perform any administrative action on the database, including data modification actions. Therefore, this role is not the correct answer.
userAdmin -> Incorrect. The userAdmin role provides the ability to create, remove, and manage users and roles on the current database. However, this role does not provide the ability to modify the database‘s design or structure, nor does it permit any data modification actions on existing data.
Question 2:
What is the purpose of the nojournal option in the context of MongoDB server
administration?
A. The nojournal option is used to configure the MongoDB server to not use journaling for write operations.
B. The nojournal option is used to configure the MongoDB server to use journaling for all write operations.
C. The nojournal option is used to configure the MongoDB server to not use write operations.
D. The nojournal option is used to configure the MongoDB server to use journaling only for critical write operations.
Answer: A
Explanation:
The nojournal option is used to configure the MongoDB server to not use journaling for write operations. -> Correct. Journaling is a key feature of MongoDB that provides durability and consistency guarantees for write operations. When journaling is enabled, MongoDB writes all changes to a journal before committing them to the data files on disk. This provides a record of the changes that have been made, and allows the MongoDB server to recover from crashes or unexpected shutdowns by replaying the journal.
The nojournal option is used to configure the MongoDB server to not use journaling for write operations. When journaling is disabled, write operations are committed directly to disk without being written to a journal first. This can result in improved write performance, but it also means that the MongoDB server will not be able to recover from crashes or unexpected shutdowns, and data loss may occur. As a result, the nojournal option is generally not recommended for production deployments, and should only be used in testing or development environments where data consistency and durability are not critical requirements.
Question 3:
What is an arbiter in replica set?
A. Special type of replica set member. An arbiter has a copy of the data set and can‘t become a primary but it participates in elections for primary.
B. Special type of replica set member. An arbiter doesn‘t have a copy of the data set and can become a primary.
C. Special type of replica set member. An arbiter has a copy of the data set and can become a primary.
D. Special type of replica set member. An arbiter doesn‘t have a copy of the data set and can‘t become a primary but it participates in elections for primary.
Answer: D
Explanation:
Special type of replica set member. An arbiter doesn‘t have a copy of the data set and can‘t become a primary but it participates in elections for primary. -> Correct. An arbiter is a special type of replica set member that doesn‘t have a copy of the data set and can‘t become a primary, but it participates in elections for primary. In MongoDB replica sets, an arbiter is a lightweight member that helps in achieving consensus during the election of a new primary node. The primary purpose of an arbiter is to provide a voting member in the replica set without requiring the storage resources needed for data replication. An arbiter does not store any data from the replica set. It only participates in the election process to help determine which member should become the primary node. When an election occurs, the arbiter contributes its vote to the majority calculation, which is necessary to elect a new primary. Arbiters are useful in scenarios where you want to have an odd number of voting members to avoid split-brain situations (where two equally eligible nodes both believe they are the primary). By having an arbiter, you can maintain an odd number of voting members with fewer resources, as the arbiter does not store data.
https://www.mongodb.com/docs/manual/core/replica-set-arbiter/
Question 4:
Given a flights collection that is sharded on the following shard key:
{ “airline_id“ : 1, “departure_airport“ : 1 }
Which of the following queries results in a targeted query? Select all that apply.
A. db.flights.find( { airline_id: 2946863 } )
B. db.flights.find( { departure_airport: “JFK“ } )
C. db.flights.find( { departure_airport: “JFK“, airline_id: 2946863 } )
D. db.flights.find( { airline_id: 2946863, departure_airport: “JFK“ } )
Answer: A, C, D
Explanation:
db.flights.find( { airline_id: 2946863, departure_airport: “JFK“ } ) -> Correct. This query includes the complete shard key, so it‘s targeted. MongoDB can directly route this query to the relevant shards.
db.flights.find( { airline_id: 2946863 } ) -> Correct. This query includes the “airline_id“, which is a prefix of the shard key. Therefore, it‘s a targeted query and MongoDB can route it to the relevant shards.
db.flights.find( { departure_airport: “JFK“, airline_id: 2946863 } ) -> Correct. Although the order of the fields is reversed, MongoDB is smart enough to recognize that this query includes the complete shard key and can route it to the relevant shards. Therefore, it‘s a targeted query.
db.flights.find( { departure_airport: “JFK“ } ) -> Incorrect. This query only includes the second part of the shard key and lacks the “airline_id“ which is the prefix of the shard key. Therefore, this is not a targeted query and MongoDB will broadcast it to all shards, which can be inefficient.
https://docs.mongodb.com/manual/core/sharding-shard-key/
Question 5:
When performing a MongoDB database backup, what are the key considerations to ensure data integrity and consistency? Select all correct answers.
A. Take a snapshot of the database files using the operating system‘s file system-level backup mechanism.
B. Lock the database to prevent any write operations during the backup process.
C. Use the mongodump command to create a logical backup of the data.
D. Enable the “journal“ option to ensure durability and crash recovery.
E. Perform regular consistency checks using the db.checkReplication() command.
Answer: A, C, D
Explanation:
Take a snapshot of the database files using the operating system‘s file system-level backup mechanism. -> Correct. Taking a snapshot of the database files at the file system level ensures a consistent backup of the data. It captures the state of the database at a specific point in time.
Use the mongodump command to create a logical backup of the data. -> Correct. Using the mongodump command creates a logical backup by dumping the data in a BSON format. It ensures that the backup captures the database‘s structure and contents.
Enable the “journal“ option to ensure durability and crash recovery. -> Correct. Enabling the “journal“ option is important for data durability and crash recovery. It ensures that write operations are journaled before being committed to the database, reducing the risk of data loss.
Lock the database to prevent any write operations during the backup process. -> Incorrect. Locking the database during the backup process is not recommended, as it would prevent any write operations. It would impact the availability of the database and is generally not required for a consistent backup.
Perform regular consistency checks using the db.checkReplication() command. -> Incorrect. This command is used for checking the consistency of a replica set, not for performing backups. It is unrelated to the backup process.
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Question 6:
The minimum recommended configuration for a replica set is a…
A. five member replica set - one primary and four secondary members.
B. two member replica set - one primary and one secondary member.
C. five member replica set - one primary and four secondary members.
D. three member replica set - one primary and two secondary members.
Answer: D
Explanation:
Three member replica set – one primary and two secondary members. -> Correct. A replica set is a group of MongoDB servers that maintain the same data set, providing redundancy and high availability. It consists of multiple nodes, with one primary node and one or more secondary nodes.
In a replica set, the primary node handles all write operations and the secondary nodes replicate the data from the primary node. In case the primary node fails, one of the secondary nodes automatically becomes the new primary node, ensuring continuous operation of the database.
The minimum recommended configuration for a replica set is to have three members – one primary and two secondary members. This configuration provides fault tolerance and allows for automatic failover in case the primary node becomes unavailable. With three members, the replica set can maintain a majority (2 out of 3) and elect a new primary if necessary.
https://www.mongodb.com/docs/manual/reference/replica-configuration/
Question 7:
Which method should you use to reconfigure a replica set by applying a new replica set configuration?
A. rs.initialize()
B. rs.reconfig()
C. rs.conf()
D. rs.status()
Answer: B
Explanation:
rs.reconfig() -> Correct. In MongoDB, this method is used to reconfigure a replica set by applying a new replica set configuration. This method allows you to modify various aspects of the replica set configuration, such as adding or removing members, changing member priorities, adjusting replica set settings, and more.
rs.conf() -> Incorrect. rs.conf() is used to display the current replica set configuration, but it does not have the functionality to modify or reconfigure the replica set.
rs.initialize() -> Incorrect. rs.initialize() is not a valid method in MongoDB. It does not exist as a built-in method for replica set reconfiguration.
rs.status() -> Incorrect. rs.status() is used to display the current status of the replica set, but it does not provide the ability to reconfigure the replica set.
https://www.mongodb.com/docs/manual/reference/method/rs.reconfig/
Question 8:
Complete the sentence below.
By default, all MongoDB user-created collections…
A. have an _id index.
B. have an field_id index.
C. have no index.
D. have an _object index.
Answer: B, C
Explanation:
By default, all MongoDB user-created collections have an _id index. -> Correct. This is because MongoDB, by default, creates a unique index on the _id field when a new collection is created. The _id index prevents clients from inserting two documents with the same value for the _id field.
https://docs.mongodb.com/manual/core/document/
https://docs.mongodb.com/manual/reference/method/ObjectId/
Question 9:
How can you configure the behavior of the mongos process in a MongoDB sharded cluster when it comes to handling read requests?
A. By setting the writeConcern configuration option.
B. By setting the readPreference configuration option.
C. By setting the sharding configuration option.
D. By setting the replication configuration option.
Answer: B
Explanation:
By setting the readPreference configuration option. -> Correct. In a MongoDB sharded cluster, the mongos process routes read requests to the appropriate shard(s) based on the shard key, chunk boundaries, and the desired behavior for handling read requests.
One important aspect of this behavior is the read preference, which specifies the preferred source of data for read operations. The readPreference configuration option determines the behavior of the mongos process when routing read requests to the shards in the cluster.
For example, if you want to ensure that read requests are directed to the nearest available shard, you can set the readPreference option to nearest. If you want to prioritize read requests to the primary shard in a replica set, you can set the readPreference option to primary.
It‘s important to note that the readPreference option only affects the behavior of read operations and has no impact on write operations. The writeConcern option, on the other hand, determines the behavior of the mongos process when routing write requests to the shards in the cluster.
In summary, the mongos process in a MongoDB sharded cluster can be configured to handle read requests in a variety of ways, and the readPreference option is an important aspect of this configuration, allowing you to specify the desired behavior for read operations in the cluster.
Question 10:
Suppose you are managing a MongoDB database for an e-commerce application with a large number of concurrent users. The database needs to be available 24/7 with zero downtime for maintenance or upgrades. What would be the best approach to ensure high availability for the MongoDB database?
A. Implement a replica set with two members.
B. Implement a replica set with three members and automatic failover.
C. Implement a sharded cluster with multiple replica sets.
D. Implement a single standalone MongoDB instance.
Answer: B
Explanation:
Implement a replica set with three members and automatic failover. -> Correct. A replica set in MongoDB is a group of MongoDB instances that maintain the same data set, providing redundancy and automatic failover in case of a primary server failure. Implementing a replica set with three members and automatic failover ensures high availability for the MongoDB database, as the primary member can automatically fail over to one of the secondary members in the event of a failure, minimizing downtime and ensuring that the database remains available to users.
Implement a single standalone MongoDB instance. -> Incorrect. A single standalone MongoDB instance, does not provide any redundancy or automatic failover, and may result in significant downtime in case of a failure.
Implement a replica set with two members. -> Incorrect. A replica set with two members, provides some redundancy but may result in some downtime in case of a failure, as the remaining secondary member will need to be promoted to primary.
Implement a sharded cluster with multiple replica sets. -> Incorrect. A sharded cluster with multiple replica sets, provides high scalability and availability, but may result in more complex administration and management.
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SkillCertPro offers detailed explanations to each question which helps to understand the concepts better.
It is recommended to score above 85% in SkillCertPro exams before attempting a real exam.
SkillCertPro updates exam questions every 2 weeks.
You will get life time access and life time free updates
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